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Biomedical subjects

J M Carney

Publications and source records attributed to J M Carney.

At least 55 records · Page 3Linked to original sources
PubMed1995

Direct evidence of oxidative injury produced by the Alzheimer's beta-amyloid peptide (1-40) in cultured hippocampal neurons.

The beta-Amyloid peptide (A beta) is hypothesized to mediate the neurodegeneration seen in Alzheimer's disease. Recently, we proposed a new hypothesis to explain the toxicity of A beta based on the free-radical generating capacity of A beta. We have recently demonstrated using electron paramagnetic resonance (EPR) spectroscopy that A beta (1-40) generates free radicals in solution. It was therefore suggested that A beta radicals can attack cell membranes, initiate lipoperoxidation, damage membrane proteins, and compromise ion homeostasis resulting in neurodegeneration. To evaluate this hypothesis, the ability of A beta to induce neuronal oxidation, changes in calcium levels, enzyme inactivation, and neuronal death were compared with the ability of A beta to produce free-radicals. Using hippocampal neurons in culture, several methods for detection of oxidation were utilized such as the conversion of 2,7-dichlorofluorescin to 2,7-dichlorofluorescein, and a new fluorescence microscopic method for the detection of carbonyls. The ability of A beta to produce free-radicals was determined using EPR with the spin-trapping compound N-tert-butyl-alpha-phenylnitrone. Consistent with previous studies, we found that preincubation of A beta increased the toxicity of the peptide. There is a strong correlation between the intensity of radical generation by A beta and neurotoxicity. The highest neuronal oxidation and toxicity was seen at a time when A beta was capable of generating the most intense radical signal. Furthermore, little oxidation and toxicity was seen when cultures were treated with freshly dissolved A beta, which did not generate a detectable radical signal. These data are consistent with the hypothesis that free-radical-based oxidative damage induced by A beta contributes to the neurodegeneration of Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed1995

Locomotor stimulant effects of cocaine and novel cocaine analogs in DBA/2J and C57BL/6J inbred mice.

The current study compared the potencies of cocaine and a series of substituted phenyltropane analogs of cocaine in stimulating locomotor activity in two genetically distinct strains of mice previously shown to differ in their locomotor responsiveness to cocaine. In addition, these compounds were compared for their abilities to induce stereotyped behaviors in naive and cocaine-pretreated mice. All of the analogs tested were more potent locomotor stimulants than cocaine in both strains. Interstrain differences in the locomotor stimulant efficacy of RTI-31 and RTI-98 parallel those of cocaine, with DBA/2J mice being stimulated to a greater extent than C57BL/6J mice at maximally active doses. Significant differences exist in the onset and duration of action among cocaine and several analogs. Whereas the action of cocaine peaks in the first 10 min after injection and thereafter rapidly declines, the stimulant effects of RTI-31, RTI-98, and RTI-113 are maximal at 30-40 min and remain consistent through 60 min postinjection. The current results are discussed in the context of previously published reports of genotype-dependent differences in behavioral responsiveness to cocaine in the DBA/2J and C57BL/6J strains.

Animals↗
PubMed1995

Ischemia/reperfusion-induced changes in membrane proteins and lipids of gerbil cortical synaptosomes.

The effects of transient bilateral carotid occlusion on the physical state of synaptosomal membrane proteins and lipids were studied in adult and aged gerbils employing electron paramagnetic resonance. Transient ischemia was produced in adult and aged gerbils by bilateral occlusion of the common carotid arteries with reperfusion times ranging from 0 to 24 h. Synaptosomes of the cerebral cortices were isolated and labeled with a protein-specific spin probe (2,2,6,6-tetramethyl-4-maleimido-piperidine-1-oxyl) and a lipid-specific spin probe (5-doxylstearic acid). Changes in the physical state of the protein peaked at 60 min reperfusion for both adult and aged gerbil models, with a more intense change in aged, but did not return to control values by 24 h. A biphasic change occurred with the lipid-specific label in both the aged and adult models. The onset of the first phase of change occurred at an earlier time (30 min reperfusion) for aged gerbil tissue than for adult tissue (between 3 and 6 h reperfusion), while the second phase of change occurred at 12 h reperfusion for both adult and aged. These results are consistent with the hypothesis that protein oxidation and lipid peroxidation are direct results of free radicals produced during the reperfusion following ischemia and that protein oxidation may be intensified by peroxidation of the surrounding lipids. Phospholipase A2 activation is implicated to cause changes in membrane phospholipid organization as seen in these studies.

Animals↗
PubMed1995

Prevention of ischemia/reperfusion-induced alterations in synaptosomal membrane-associated proteins and lipids by N-tert-butyl-alpha-phenylnitrone and difluoromethylornithine.

Previous studies in our laboratory demonstrated the alteration in the physical state of synaptosomal membrane lipids and proteins in ischemia/reperfusion injury using selective spin labels and electron paramagnetic resonance spectroscopy [Hall et al. (1995) Neuroscience 61, 84-89]. Since many investigations have provided evidence for free radical generation during ischemia/reperfusion injury, we investigated whether a free radical scavenger would prevent the membrane damage, in gerbils. Further, experiments to determine if a secondary effect of polyamine generation at 14 h reperfusion could be blocked by this free radical scavenger or by an inhibitor of ornithine decarboxylase were also carried out. The alterations in synaptosomal membrane integrity observed during ischemia/reperfusion injury were selectively neutralized by treatment with the free radical spin trap N-tert-butyl-alpha-phenylnitrone or an inhibitor of ornithine decarboxylase, difluoromethylornithine. Administration of N-tert-butyl-alpha-phenylnitrone prior to ischemia totally abrogated both lipid and protein alterations observed at 1 and 14 h reperfusion. Pretreatment with difluoromethylornithine neutralized only the 14 h change in lipid label motion. Treatment with N-tert-butyl-alpha-phenylnitrone at 6 h post ischemia showed only a slight attenuation of the 14 h lipid effect and no change in the protein effect. Difluoromethylornithine treatment at 6 h post ischemia negated the 14 h ischemia/reperfusion injury-induced lipid effect and had no effect on the protein change. These data support previous suggestions that free radicals and polyamines play a critical role in neuronal damage and cell loss following ischemia/reperfusion injury and that the polyamine effect is dependent upon free radical generation during ischemia/reperfusion injury.

Analysis of Variance↗
PubMed1995

Enhancement of beta-amyloid peptide A beta(1-40)-mediated neurotoxicity by glutamine synthetase.

The beta-amyloid peptide (A beta), a main constituent in both senile and diffuse plaques in Alzheimer's disease brains, was previously shown to be neurotoxic and to be able to interact with several macromolecular components of brain tissue. Previous investigations carried out in our laboratory demonstrated free radical species formation in aqueous solutions of A beta(1-40) and its C-end fragment, A beta(25-35). Toxic forms of A beta rapidly inactivate the oxidation-sensitive cytosolic enzyme glutamine synthetase (GS). In this regard, we suggested and subsequently demonstrated that A beta radicals can cause an oxidative damage of cell proteins and lipids resulting in disruption of membrane functions, enzyme inactivation, and cell death. Because GS can be a substrate for A beta-derived oxidizing species, the present study was conducted to determine if GS could protect against A beta neurotoxicity. In contrast to this initial hypothesis, we here report that GS significantly enhances the neurotoxic effects of A beta(1-40). The A beta-mediated inactivation of GS was found to be accompanied by the loss of immunoreactive GS and the significant increase of A beta(1-40) neurotoxicity.

Amyloid beta-Peptides↗
PubMed1995

Brain regional correspondence between Alzheimer's disease histopathology and biomarkers of protein oxidation.

Four biomarkers of neuronal protein oxidation [W/S ratio of MAL-6 spin-labeled synaptosomes, phenylhydrazine-reactive protein carbonyl content, glutamine synthetase (GS) activity, creatine kinase (CK) activity] in three brain regions [cerebellum, inferior parietal lobule (IPL), and hippocampus (HIP)] of Alzheimer's disease (AD)-demented and age-matched control subjects were assessed. These endpoints indicate that AD brain protein may be more oxidized than that of control subjects. The W/S ratios of AD hippocampal and inferior parietal synaptosomes are 30 and 46% lower, respectively, than corresponding values of tissue isolated from control brain; however, the difference between the W/S ratios of AD and control cerebellar synaptosomes is not significant. Protein carbonyl content is increased 42 and 37% in the Alzheimer's HIP and IPL regions, respectively, relative to AD cerebellum, whereas carbonyl content in control HIP and IPL is similar to that of control cerebellum. GS activity decreases an average of 27% in the AD brain; CK activity declines by 80%. The brain regional variation of these oxidation-sensitive biomarkers corresponds to established histopathological features of AD (senile plaque and neurofibrillary tangle densities) and is paralleled by an increase in immunoreactive microglia. These data indicate that senile plaque-dense regions of the AD brain may represent environments of elevated oxidative stress.

Aged↗
PubMed1995

An animal model and computer-controlled surface pressure delivery system for the production of pressure ulcers.

Pressure ulcers continue to be a major health care problem. This paper describes an animal model and surface pressure delivery system for the production of experimentally derived pressure ulcers. A method for inducing dermal pressure lesions on the fuzzy rat was developed using a computer-controlled displacement column which produced a constant tissue interface pressure. The pressure column consists of a force transducer located between two 0.5-in (1.27-cm) diameter metal cylinders. The desired cutaneous pressure is maintained by a computer-controlled miniature stepper motor which displaces the column with the aid of interactive software. The force transducer signal is converted from analog to digital form, amplified, and recorded. Blood perfusion is monitored using a laser Doppler flowmeter (located in the tip of the column) during the application of pressure. The application of 145 mmHg pressure for 5 consecutive 6-hr sessions resulted in a greater than 90% incidence of pressure ulcers. The implications of our model and contributions of earlier animal models are discussed. This model provides a tightly controlled and measured environment making possible the scientific study of ulcer development and the evaluation of potential preventative or curative compounds.

Animals↗
PubMed1994

Aging- and oxygen-induced modifications in brain biochemistry and behavior.

In summary, the work presented here has shown accumulation of oxidized protein with age in an animal aging model. In gerbil brain, this accumulation is associated with (1) decreased activity of oxidatively sensitive enzymes creatine kinase and glutamine synthetase; (2) decreased function of particular cytoskeletal proteins; and (3) decreased performance in a radial-arm maze task. Manipulations shown to increase the presence of reactive oxygen species in the brain increase oxidized protein, decrease the index enzyme activities and cytoskeletal protein defects, and worsen performance deficits. Moreover, intervention designed to quench ROS-mediated reactions decrease oxidized protein levels, and nearly normalize index enzyme activities and associated behavioral deficits. The precise connections between the performance deficits and protein measures are probably highly complex and likely to remain obscure for now. Currently, the behavioral measures serve as a marker for the functional consequences of the protein alterations. Our studies in humans have shown oxidized protein accumulation with age and a differential decrease of glutamine synthetase activity in the frontal lobe in AD. Further preliminary results in AD autopsy material show a striking correlation between the distribution of index enzyme inactivation and the known intensity distribution of AD pathology. These findings support the hypothesis that inability to restrain age- or pathology-related increases in local ROS activity can result in AD.

Aging↗
PubMed1994

In vitro and in vivo activity of a novel series of radical trapping agents in model systems of CNS oxidative damage.

Many laboratory and clinical studies suggest that oxygen radical formation and resultant cell damage contribute to CNS injury following stroke and neurotrauma. Accordingly, antioxidants represent a viable therapeutic approach for management of CNS oxidative damage. Recently, several investigators have reported that the spin trap PBN protects against stroked-induced damage and reduces aging-associated neurological deficits. We have prepared and tested a cyclic analog of PBN, MDL 101,002, in a number of in vitro and in vivo assays designed to assess its neuroprotective properties. MDL 101,002 was found to be an effective .OH trap, to inhibit lipid peroxidation, and to decrease infarct size in a gerbil model of stroke. These results further indicate that oxidative damage arising from stroke contributes to infarct formation, and that spin traps are effective in ameliorating ischemia and reperfusion-induced CNS injury.

Animals↗
PubMed1994

A model for beta-amyloid aggregation and neurotoxicity based on free radical generation by the peptide: relevance to Alzheimer disease.

beta-Amyloid is a 39- to 43-amino-acid neurotoxic peptide that aggregates to form the core of Alzheimer disease-associated senile (amyloid) plaques. No satisfactory hypothesis has yet been proposed to explain the mechanism of beta-amyloid aggregation and toxicity. We present mass spectrometric and electron paramagnetic resonance spin trapping evidence that beta-amyloid, in aqueous solution, fragments and generates free radical peptides. beta-Amyloid fragments, at concentrations that previously have been shown to be neurotoxic to cultured neurons, can inactivate oxidation-sensitive glutamine synthetase and creatine kinase enzymes. Also, salicylate hydroxylation assays indicate that reactive oxygen species are generated by the beta-amyloid-(25-35) fragment during cell-free incubation. These results are formulated into a free radical-based unifying hypothesis for neurotoxicity of beta-amyloid and are discussed with reference to membrane molecular alterations in Alzheimer disease.

Alzheimer Disease↗
PubMed1994

Detection of oxidation products in individual neurons by fluorescence microscopy.

In the study of the central nervous system, it is necessary to address mechanisms by which cells are injured. In vitro investigations using cells in culture allow sharply focused mechanistic questions to be addressed; however, these studies have often been limited by the sensitivity constraints of assays. Many assays for oxidative products require large amounts of cells that must be disrupted. The extent of oxidation in individual cells is therefore unknown and the results yield an average among different cell types. This is inconvenient in cultures of the nervous system which often have multiple cell types. Using a newly developed method for visualizing oxidation products in individual cells, we have examined oxidation in neurons in culture. The method uses a hydrazide, biotin-4-amidobenzoic hydrazide, to bind carbonyls generated from oxidation. Biotin is detected by streptavidin conjugated with a fluorescent dye. Neurons in culture were exposed to 0.1 to 100 microM ferrous sulfate and fluorescence was visualized and quantitated using confocal laser microscopy. Low levels of oxidation (0.1 microM ferrous sulfate) were easily detected with this method. Iron concentration and fluorescence intensity correlated highly (r = 0.991). As an indicator of the sensitivity of this new method, carbonyl content in the cultures was also quantitated using the 2,4-dinitrophenylhydrazine assay (DNPH). The DNPH assay failed to detect the low levels of oxidation which were detected by the biotin-4-amidobenzoic hydrazide method. Fluorescence intensity partially paralleled loss of neuronal viability. Low concentrations of iron (0.1 and 1.0 microM) did not produce significant neuronal death; however, higher concentrations (10 and 100 microM) produced 19 and 53% neuronal loss, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Role of protein oxidation in aging and in age-associated neurodegenerative diseases.

Aging and age-associated neurodegenerative diseases have been proposed to be the result of changes in a in anti-oxidant status and in the production of reactive oxygen species. Studies in humans have demonstrated a significant increase in oxidized protein from brains of neurological normals and from individuals with different neurological diseases (Alzheimer's, Parkinson's and Huntington's Disease). Preclinical models of these conditions and of cerebral ischemia demonstrate the primary role of protein oxidation in the initial steps of these neurodegenerative diseases. Aging is a risk factor in the development of these diseases and is also associated with a decrease in the anti-oxidant defense systems of the brain. It is proposed that free radicals play a primary role in the initiation of those biochemical events that ultimately lead to the death of the neuron.

Aging↗
PubMed1994

Comparison of cocaine and GBR 12935: effects on locomotor activity and stereotypy in two inbred mouse strains.

The current study compares the acute and long-term effects of GBR 12935 and cocaine on locomotor activity and stereotypy in two genetically distinct strains of mice. Although cocaine stimulated locomotor activity maximally in both strains at 32 mg/kg, a single injection of cocaine stimulated locomotion to a greater degree in DBA/2J mice than in C57BL/6J mice. In contrast, GBR 12935 elevated locomotion to a greater extent in C57BL/6J mice at the maximally active dose of 10 mg/kg. The stimulant effects of cocaine diminished to near control levels in DBA/2J mice upon repeated injections, whereas cocaine-induced locomotion remained relatively consistent in C57BL/6J mice. Locomotor stimulation by GBR 12935 remained consistent in both strains with repeated injections. DBA/2J mice became sensitized to cocaine-induced stereotypy with repeated injections. Cocaine induced no stereotypy in C57BL/6J mice on any test day. No stereotypies were induced by GBR 12935 in either strain on any test day. Moreover, no cross-sensitization between cocaine and GBR 12935 was observed. These results demonstrate differences in the behavioral effects of two dopamine uptake inhibitors, and suggest that genetically controlled factors other than dopamine uptake inhibition contribute to the acute and adaptive behavioral responses to cocaine.

Animals↗
PubMed1994

Sensitization to stereotypy in DBA/2J but not C57BL/6J mice with repeated cocaine.

The present study investigated the effects of seven repeated daily injections of 32 mg/kg cocaine on stereotyped behaviors (repetitive locomotion, rearing, and head bobbing) in two genetically distinct strains of mice. An initial injection of cocaine induced no stereotypy in either DBA/2J or C57BL/6J mice. Following the fourth daily injection, cocaine induced stereotypies in DBA/2J mice (11.33 +/- 4.40) compared to saline controls (2.67 +/- 1.54). Cocaine-induced stereotypy in DBA/2J mice was further enhanced following the seventh daily injection (19.83 +/- 4.39) as compared to saline controls (0.67 +/- 0.54). No cocaine-induced stereotypy was observed in C57BL/6J mice following any injection. Eighth day saline challenges of cocaine-sensitized mice did not induce stereotypy. Eighth day cocaine challenges of saline-treated mice induced no stereotypy in either strain. The current study demonstrates that sensitization to cocaine can be influenced by genotype and suggests that genetically defined animals may be useful in elucidating mechanisms underlying sensitization and tolerance to cocaine.

Animals↗
PubMed1994

Histopathology of pressure ulcers as a result of sequential computer-controlled pressure sessions in a fuzzy rat model.

This study describes the sequential histopathological changes that occur in the development of pressure ulcers experimentally induced in the fuzzy rat model. Computer-controlled pressure was applied for six hours at a maximum of five sessions, to skin over the greater trochanter of anesthetized rats. Lesions were similar, but more pronounced after the third, fourth, and fifth sessions as compared to the first or second sessions. Lesions developed first in the muscle rather than the dermis or epidermis. The lesion most often associated with pressure was necrosis of the panniculus carnosus muscle, often accompanied by damage to underlying adipose tissue. Recurrent pressure results in increasingly severe damage to the vascular system and parenchyma, consistent with an ischemia/reperfusion insult initiated through a free radical mechanism.

Animals↗
PubMed1994

Genetic analysis of sensitization and tolerance to cocaine.

The present study investigated the effects of acute and repeated administration of cocaine (1.0-56.0 mg/kg) on locomotor activity in the genetically distinct DBA/2J and C57BL/6J inbred strains of mice. In addition, quantitative trait loci analysis of the effects of acute and repeated cocaine in 16 BXD recombinant inbred strains was used to provisionally detect and map minor gene loci which associate with cocaine responsiveness. Whereas locomotor activity was elevated maximally in both strains by 32 mg/kg of cocaine, DBA/2J mice were stimulated to a much greater extent than C57BL/6J mice. The stimulant effects of cocaine were diminished to control levels in DBA/2J mice after repeated daily injections, whereas cocaine-induced locomotion remained consistent in C57BL/6J mice throughout the 7-day testing period. Emergence of stereotyped behavior with repeated daily injections of 32 mg/kg of cocaine was observed in DBA/2J but not C57BL/6J mice. No differences in brain cocaine levels were found between the DBA/2J and C57BL/6J strains after acute or repeated injections. Quantitative trait loci analysis indicated significant associations of differences in cocaine responsiveness with marker loci on several chromosomes in the BXD recombinant inbred series. Those marker loci associated with the acute cocaine response were in most cases different from those markers associated with long-term responses. The current results demonstrate that genotype-dependent variation exists in behavioral responsiveness to cocaine in mice and suggest that the acute and long-term responses to cocaine may be under the control of separate sets of genes.

Animals↗
PubMed1993

Near-infrared spectrophotometric monitoring of stroke-related changes in the protein and lipid composition of whole gerbil brains.

Strokes are a critical problem in the U.S. that affect more than 500,000 people annually. Research into the causes of stroke and testing of drug therapies to reduce ischemic and postischemic damage to the brain is frustrated by an inability to continuously follow the physical and chemical events that occur during ischemia and reperfusion in vivo. Near-IR spectrometry is used in this paper to observe stroke-induced changes in the lipids and proteins of whole brain samples and in intact subjects. The examination of whole brains is made possible by a combination of hardware and software techniques designed to make the sample presentation to the spectrometer more reproducible. Near-IR spectrophotometry of brain tissue discriminates between adult (3-4 months of age) and aged (18-20 months of age) brains as well as between brains exposed to 5- and 10-min ischemia. The near-IR analytical method has many applications in aging and stroke research, including the noninvasive determination of age from brain spectra obtained transcranially, simultaneous multicomponent analysis of lipids and proteins, and quantification of edema.

Aging↗